1. Field of the Invention
This invention relates to silylated polymers having mixed alkoxy groups on the silyl portion thereof, methods of their preparation, and compositions and reaction products formed therefrom. These alkoxysilylated polymers can be crosslinked when exposed to atmospheric moisture to become useful elastomers, sealants or adhesives. The presence of different alkoxy groups on the silicon atoms can control the cure speeds of these silylated polymers.
2. Background of Related Technology
Alkoxysilylated polymers, in the presence of a catalyst, can be crosslinked by atmospheric moisture under ambient conditions. Compositions based on these type of polymers are often referred to as RTV sealants (or adhesives). The most well known example is RTV silicone sealants.
Crosslinking of alkoxysilylated polymers involves hydrolysis and condensation reactions of the alkoxylsilyl group. The cure speed of compositions prepared therefrom has conventionally been accelerated through the use of various types and amounts of moisture cure catalysts. However, among the disadvantages of using increased amounts of such catalysts to obtain greater cure speeds are potential instability, loss of shelf life and enhanced manufacturing and material costs of such compositions.
The smaller alkoxy groups, e.g. methoxy, are ordinarily more reactive and thus better able to be displaced by another chemical entity. Therefore, methoxy groups are more desirable for obtaining moisture curable polymers having faster and/or more controlled cure speeds. Currently, however, the starting materials for making many lower alkoxy group-containing polymers with a variety of backbones, such as polyethers like polypropylene oxide (“PPO”), are not readily commercially available. For example, a desirable route for making silyl-terminated PPO polymers containing alkoxy groups might include reacting an isocyanatoalkyltrialkoxysilane with an hydroxy terminated PPO. However, presently trimethoxysilyl-terminated isocyanatoalkyl compounds are not widely commercially available.
Thus, there is a need for a method of conveniently producing a moisture curable composition which includes a curable polymer having a mixture of different alkoxy groups present, at least one of which being a methoxy group, whereby controlled moisture cure speed is obtained.